CN1193390A - Position feedback system for volume holographic storage media - Google Patents

Position feedback system for volume holographic storage media Download PDF

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Publication number
CN1193390A
CN1193390A CN97190501A CN97190501A CN1193390A CN 1193390 A CN1193390 A CN 1193390A CN 97190501 A CN97190501 A CN 97190501A CN 97190501 A CN97190501 A CN 97190501A CN 1193390 A CN1193390 A CN 1193390A
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Prior art keywords
data page
medium
servo block
servo
angle
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CN97190501A
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Chinese (zh)
Inventor
纳萨·J·哈伊斯
詹姆斯A·汉森
克里斯托福·M·卡彭特
小威廉·R·阿金
理查德·M·欧里奇
兰斯·D·比兹利
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Quantum Corp
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Quantum Corp
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/26Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
    • G03H1/28Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique superimposed holograms only
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/22Processes or apparatus for obtaining an optical image from holograms
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0065Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/007Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
    • G11B7/00772Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track on record carriers storing information in the form of optical interference patterns, e.g. holograms
    • G11B7/00781Auxiliary information, e.g. index marks, address marks, pre-pits, gray codes

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Holo Graphy (AREA)
  • Optical Recording Or Reproduction (AREA)

Abstract

A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g. voice coil motor) which respond to position feedback information and adjust the angular position of the reference angle of a reference beam to maximize SNR by reducing crosstalk, thereby improving storage capacity.

Description

The position feedback system of volume holographic storage media
The present invention relates to principal and interest storage medium and hologram storage method.More specifically, the present invention relates in photorefractive media with hologram form record data with from method of reproducing data wherein, this hologram comprises the hologram that contains position feedback information.
Think always that for many years the potentiality of body holographic memory are that digital memory capacity is big in the photorefractive media, message data rate is fast and the access time short.Latest developments in material and holographic memory element field have made this prospect near realizing that data storage capacity is a terabyte, and data transfer rate surpassed for 1 GB/second, and random access time is less than 100 μ s.
Photorefractive material has the character that photon-induced refractive index changes.Holographic memory can realize by carrying image beam and propagation and the record of reference beam in photorefractive media.The optical interference pattern that forms makes the space refractive index in the whole volume of holographic media modulated.In photorefractive media, as at LiNbO 3In (lithium niobate), because the migration of photoexcited electron and capture and produce internal electric field and generate electrooptical effect has produced the space refractive-index grating.When using light beam irradiates this medium identical with the reference beam that produces refractive-index grating, this light beam is diffraction in such a way, reproduces the wavefront that carries original image.
In typical hologram memory system, as shown in Figure 1, light beam 24 and reference beam 22 that the relevant homogeneous beam that penetrates from light source 11 can be divided into by beam splitter 12.Utilize spatial light modulator (SLM) 14 to convert object beam 24 to light signal.Object beam 24 and reference beam 22 are by converging optical element 16 and 17, and the meeting coalescence shines light and sells off on the prosperous body 18, produce the conoscope image that body distributes in crystal 18, and this conoscope image is recorded as the form of refractive-index grating, or is referred to as hologram.Be imaged on identical reference beam 22 irradiation crystal 18 and with the light signal of diffraction and can reproduce the good hologram of record on the detector array 19, detector array converts light signal to electric signal.
Utilize various forms of multiplexing techniques, multiplexed as angle, wavelength multiplexing or the like, multiplex hologram can write and be stored in the crystal 18, the corresponding data page of each hologram.Adopt the angle multiplexing technique, each hologram is to write with different reference light velocity incident angles.The size of this angle changes with the true form and the material of crystal.Usually, difference is 50 microradians between two angles.The change of angle, or keep object beam and reference beam angle constant with mechanical means translation crystal 18, or control reference beams with converging optical element 16 and 17, the reference beam angle on the crystal is incided in change.Adopt the wavelength multiplexing technology, reference beam is fixed on a certain angle, to each data page, changes optical source wavelength and notes each hologram.
A restriction of the potential advantage of constraint holographic recording is that the hologram that record is good is metastable (impermanency).When a plurality of holograms be in order but be not partitioned record in the identical volume of crystal the time, generally be referred to as " overlapping " record, the hologram of trailer record to write in the past the hologram diffraction efficiency to reduce be heterogeneous.Therefore, " writing " process is to have reduced the intensity of former recorded hologram after repeatedly writing to the destruction that the adjacent holograms that writes down causes in the past.Similarly, " read " process of zone under the reference beam irradiation also can make the electric charge redistribution that constitutes recorded hologram.This just causes photographic fixing and the development of more permanent holograms technology of developing.For example, the hologram made from the electron charge figure can be made nonvolatilly by heating this crystal, and the heating crystal causes the ion redistribution, has offset space charge variation in the crystal.Crystal cooling after this, ion enters trap, forms nonvolatil variations in refractive index ion grating.
Another restriction of constraint holographic recording potential application is, what occur in the hologram reconstruction process crosstalks, crosstalk limits the information density and the memory capacity of crystal.Because Prague selectivity characteristic of reading light, memory image or data page can reproduce from other pages or leaves of overlapping record independently.As discussed earlier, use and shine this recording medium with the reference beam of the identical wavelength of document image and can finish reproduction.Yet, though bragg selectivity has guaranteed the reconstruction of image relevant with specific reference wavelength maximum diffraction efficiency being arranged, other storage map storages also can be reproduced, owing to Prague mismatch produces distortion and low diffraction efficiency.For fear of crosstalking of this form, angle intervals between the different holograms or wavelength interval must be accurately corresponding to the relevant sinc function zero-points of Prague matching condition.Will reduce signal to noise ratio (S/N ratio) (SMR) with some deviations of desired angle.Consequently, or the branch rate of reduction image, or the memory capacity of mini system.
Propose a lot of suggestions and attempted to overcome this capacity limit.Yet these suggestions do not utilize the closed loop position feedback system in data page retrieval, and this feedback system is to crosstalk and accurate angle orientation makes tracer signal that maximum SNR be arranged by reduction.In addition, more dizzy suggestions do not utilize the closed loop position feedback system, with permanent holograms with in metastable hologram is combined in identical recording areas.Therefore, unsolved so far difficulty still needs a kind of hologram recording method in photorefractive media, it provides position feedback system, and crosstalking by reduction makes tracer signal that maximum SNR be arranged, and is applicable to the multiplexed and two kinds of technology of wavelength multiplexing of angle.
General purpose of the present invention is to propose a kind of hologram recording method in photorefractive media, and this method overcomes the restriction and the shortcoming of prior art.
Specifically, an object of the present invention is, propose a kind of hologram recording method in photorefractive media, it has one to crosstalk by reduction and to make tracer signal that the position feedback system of maximum S R be arranged.
Another object of the present invention is, proposes a kind of hologram recording method in photorefractive media, and wherein position feedback system is applicable to the multiplexed and two kinds of technology of wavelength multiplexing of angle.
The 3rd purpose of the present invention be, proposes a kind of hologram recording method in photorefractive media, and it has a position feedback system that permanent holograms is combined with metastable hologram.
According to principle of the present invention, hologram recording method is at first in photorefractive media, as at LiNbO 3Record a plurality of servo blocks (servo block) in the crystal.Each servo block is determined by five spot pattern.Utilize the same area that object beam and reference beam shine crystal simultaneously to make servo block.Be defined as reference angle with reference to the light velocity to the incident angle of plane of crystal.Servo block provides position feedback during reproduction is stored in data page in the crystal, can make the data page of reproduction that maximum SNR is arranged.Several servo blocks are also noted on such reference angle increment, this is the minimum angular separation of crystal half with reference to increment, the minimum angular separation of crystal is determined by the physical size of crystal, the method of utilizing the professional to know, as heat crystal, servo block is made can not wipe (fixing).In five light classes each is recorded in the image space identical with data page, makes that position feedback information and data page are retrieved simultaneously during hologram reconstruction.
Then, adopting uses the same method is recorded in data page in the identical image space of crystal,, shines crystal simultaneously with the object beam and the reference beam that carry image that is.Several data are noted on such reference angle increment, and this reference angle increment is the minimum angular separation of crystal.During data page retrieval, be sent to reverberator steady arm, for example voice coil motor from the position feedback information of servo block.Steady arm is with the position, angle of the rotation mode accommodation reflex mirror reference angle with the fine setting reference beam, makes tracer signal that maximum SNR be arranged thereby crosstalk by reduction.
Fig. 1 is the synoptic diagram that adopts photorefractive crystal typical prior art holographic recording system.
Fig. 2 is a process flow diagram of realizing each step of hologram recording method of the present invention.
Fig. 3 is the hologram recording method according to the principle of the invention, and a servo block embodiment that position feedback is provided is described.
Fig. 4 a to Fig. 4 e is according to the principle of the invention, five figures of key diagram 3 servo blocks.
Fig. 5 is the curve map of data page amplitude as reference beam incident angle function.
Fig. 6 is the curve map of servo block amplitude as reference beam incident angle function.
Fig. 7 is the curve map of the difference of Fig. 6 function of position as the incident angle function.
Fig. 8 is the curve map of linear orientation function as reference beam incident angle function.
Fig. 9 function of servo block sinc image intensity that draw as the reference beam incident angle.
Figure 10 is used to write down holographic recording system synoptic diagram with reconstructing hologram according to the present invention.
Fig. 2 draws and realizes the process flow diagram of each step of hologram recording method of the present invention.These steps comprise: determine the minimum angular separation 100 of crystal, and record servo block 200 in crystal, the heating crystal makes servo block fix 300, and the crystal quenching temperature drops to room temperature 400, and record data page or leaf 500 in crystal reproduces the data page 600 that writes down.
Before any hologram of record, the first step 100 determines that rolling makes the minimum of crosstalking with the required minimum angular separation of holographic recording in the photorefractive crystal.For the professional, derive the details of determining minimum angular separation formula and know.Specifically, these details are discussed in people's such as JohnH.Hong article and were described, and exercise question is " body hologram memory system: method and structure ", Oplical Engineering (optical engineering), Vol.34, No.8, in August nineteen ninety-five, it is for reference to enclose this article in the lump.The minimum angular separation that people such as Hong determine is following formula,
θ=λcosθo/nLsin(θr+θo) (1)
λ=signal wavelength wherein, the n=crystal refractive index, L=crystal thickness, θ r=reference beam are with respect to the incident angle of Z axle, and θ o=object beam is with respect to the incident angle of Z axle.θ r can determine according to the layout of converging optical element and crystal.Formula (1) is applied to embodiment illustrated in fig. 4, θ o=0 wherein, θ r is about 33, then formula (1) is reduced to
θ=1.88λ/nL (2)
In case minimum angular separation is decided, then can write down servo block according to the conventional method that the professional knows.The record of servo block adopts preferred holographic recording system 30 shown in Figure 10.System 30 comprises: the light source 31 that produces signal, beam splitter 32, it is divided into object beam 44 and reference beam 42 to signal 43, rotatable mirror 33, it has two (2) the individual degree of freedom that change reference angle θ r, catoptron 35, spatial light modulator (SLM) 34, it is transformed into light signal by modulator light beam 44 with electric signal, convergent lens 36 and 37 is used for the photorefractive crystal 38 of recorded hologram, detector array 39, voice coil motor (VCM) 41, it is a rotating mirror 31 to the response that detector array 39 detects position feedback information.SLM34 has 1.0 " * 0.8 " to observe the district approximately, provides 640 * 480 pixel regions to come the modulator light beam approximately.Detector array 39 can be any known device, and as charge-coupled device (CCD), it has 0.5 " * 0.4 " to observe the district approximately, and 1134 * 486 pixel regions are provided approximately.Crystal 38 is Fe-LiNbO 3, discoid, about 2mm is thick, and diameter is about 70mm.
According to common hologram recording method,, form the interference grating in the crystal 38, thereby in crystal 38, note each servo figure with object beam 44 that carries servo figure and reference beam 42 irradiations that specific reference angle is arranged.
In a preferred embodiment, each servo block is by five figure A of light class shown in Figure 3, B, C, D, E defined.The different position, angle of reference beam is represented in each spot intensity and combination thereof in five light classes, and position feedback information is provided.Embodiment as shown in Figure 3, five light classes are positioned at the external margin of data field, and the data field of representing among Fig. 3 is a quadrilateral area of symmetry.In this embodiment, five hot spots are arranged to like this, determine that distance is the longest between a pair of light class of each servo block in five servo blocks, thereby optimize the data field that is retrieved.Servo block is with there being the reference beam of one degree of freedom (X-axis) to represent among Fig. 3, with the Ax of band shade, and Bx, Cx, Dx, Ex represents.Make the Ay of following target reference beam with Y-axis with the band shade, By, Cy, Dy, Ey represents.Be familiar with these professional people and know, can adopt other forms of five figures, comprise other arrangement, the diverse location of light class and the number of hot spot.
Along each servo block of one degree of freedom (X-axis) with five figure A-B, B-C, C-D, D-E, E-A determine, shown in Fig. 4 a to 4e.Each figure is determined a kind of form of five hot spots.For example, figure A-B is determined that by the A of light class and the B that are with shade figure B-C is determined that by the B of light class and the C that are with shade figure C-D is determined by the C of light class and the D that are with shade, D graphics-E is determined that by the D of light class and the E that are with shade figure E-A is determined by the E of light class and the A that are with shade.The image that the light class representative of band shade is strengthened, and do not represent non-enhanced image with the light class of shade.The record of each servo block is to be increment with 0.5 θ, and at-0.75 θ, figure 2 is recorded in-0.25 θ from figure 1 opening entry, or the like.To explain that as following each servo block is represented feedback information among Fig. 4 a to Fig. 4 e, can make the retrieval of each data page that maximum S R is arranged.
Fig. 6 draw five hot spots of servo block (A, B, C, D, E) curve of sinc function.Therefore, when reference beam changed in a certain angular range, each spot intensity changed thereupon in interior five hot spots of each servo people, as shown in Figure 9.As shown in this figure, each longitudinal region B1, B2 or the like is corresponding to the function of each spot intensity as incident angle.In addition, each incident angle provides one of servo block " snapshot ", i.e. the relative intensity of each hot spot in five hot spots.For example, be under the 0.25 θ situation in incident angle, hot spot C intensity maximum, and hot spot B and D show more weak image.
In case servo block is recorded in the crystal, be recorded in metastable hologram in the photorefractive media as any other, servo block can be with repeatedly shining thereafter and be wiped free of.For " fixing " servo block, unlikelyly wiped by irradiation subsequently, give crystal 38 heating according to conventional method, this step is represented with 300.Usually, Fe-LiNbO 3Be heated to about 150-200 ℃, its intermediate ion becomes movably, and the time of keeping this temperature is depended on the size of crystal.
Then, crystal 38 takes out back cooling rapidly from thermal source, turns back to environment temperature (with step 400 expression) with the air cooling.The speed of cooling depends on the thermal shock tolerance limit of crystal usually, and " fixing " process of metastable hologram is known those skilled in the art.Yet the present inventor believes, the hologram recording method that permanent holograms and metastable hologram are combined in the same record area is that other professionals are ignorant, and this is outstanding feature of the present invention.
Should be noted that during servo block is written in the recording medium detector array can not be used as the angle feedback mechanism, because recording medium lacks any reference encoder.Similar with the disk drive servo ablation process, must utilize high precision measuring system to determine the θ angle, or utilize the scrambler on the control device of light beam, or observe object beam and reference beam with certain additive method.
Those skilled in the art understand, except servo block, also can accord with so that additional position feedback information to be provided by document image space recognition in each image space.Each recognition symbol should be unique, and each image space and other image spaces are differentiated, and adopts the method for above-mentioned relevant record servo block, and identifier can be noted simultaneously with servo block or data page.In addition, identifier also can adopt above-mentioned method to be fixed.
Next step, with step 500 expression, data page is recorded in the identical image space of crystal 38 according to the conventional method of last art record servo block.In this preferred embodiment, the reference angle increment of each data page record is θ, from 0 ° of opening entry.Thereby, the data page amplitude that Fig. 5 draws three records, D1, D2, D3 is as the function of incident angle.With reference to Fig. 5 and Fig. 6, servo block hot spot B and C provide the nominal position feedback information of data page D1 simultaneously, and servo block hot spot D and E provide the nominal position feedback information of data page D2, and servo block hot spot A and B provide the nominal position feedback information of data page D3.For example, in θ=0, hot spot B and C are equicohesive, change 0.8 of normalized intensity into, and hot spot A and D are equicohesive, are about 0.1 of normalized intensity, and this situation is represented with servo figure B-C among Fig. 4 b.The pass of adjacent servo figure ties up to and illustrates the most clearly among Fig. 7, and Fig. 7 represents it is the function of the difference of bit function as incident angle.Function A-B represents sinc function poor of servo block A and B, and function B-C represents sinc function poor of servo block B and C, or the like.
As shown in Figure 7 and Figure 8, several mapping functions are present in each " the data page " center ", promptly data page demonstrate the reference angle of maximum intensity.Yet the most linear mapping function can offer the reliable position information of that data page in each data page center.Therefore, Fig. 8 function of linear orientation function that draw as incident angle θ.So between-0.25 θ and 0.25 θ, servo figure 2 and 3 offers data page 1 feedback information, between 0.75 θ and 1.25 θ, servo figure 4 and 5 offers data page 2 feedback informations, or the like.Utilize the linear segment of each mapping function, the present invention can follow the tracks of the different pieces of information page or leaf according to mode accurately.Notice that in the present embodiment the record of different servo piece is to be increment with 0.5 θ, the scope that causes the linear orientation function is 0.5 θ.Be familiar with these professional people and understand that different servo blocks can be noted, and still can retrieve the data page of maximum S R under other increments.Yet less than 0.5 θ, the scope of linear orientation function just reduces (see figure 8) as if increment.In addition, greater than 0.5 θ, linear orientation letter scope has increased, but may comprise non-linear partial as if increment.
Should be pointed out that also reference angle θ r has two degree of freedom, that is, θ r can change along directions X, also can change along the Y direction, along each increment of each direction corresponding to the different hologram in identical image space.So, as mentioned above, can be corresponding to each servo block figure of the different reference angles that change along the Y direction along vertical edge record around the image space, as shown in Figure 3.In case minimum angular separation θ decides, just can begin ablation process, the order that servo block writes is unrestricted.Important feature is, adjacent servo block exposure is under light intensity much at one, and its spacing is an increment with 0.5 θ exactly.
An improvement to system shown in Figure 1 is that the present invention comprises above-mentioned position feedback information in order to the fine setting reference angle, by the signal that writes down that reduces to crosstalk maximum SNR is arranged.
When reproducing data page (with step 600 expression), reference beam is with specific reference angle irradiation crystal.Relevant with the size of reference angle, the parts of images of data page and servo figure can produce on detector array 39.For example, reference beam is penetrated with 0.75 θ incident and is propagated on the crystal, and it is reproduced in reference angle is data page parts of images (as shown in Figure 5) and the servo figure 3,4 that O and θ write down down, the position feedback information of 5 forms (as shown in Figure 6) is crosstalked in the image of reproduction.With reference to Fig. 8, or mapping function 3-4 or mapping function 4-5 can be respectively applied for retrieve data page or leaf D1 or D2.Because position feedback information is sent to voice coil motor (VCM) 41, VCM rotates catoptron 31 to regulate reference angle.Consequently, because the data page that reproduces has maximum diffraction efficiency and maximum intensity, place SNR maximum, the minimum of crosstalking.Perhaps, reference beam is with 1.00 θ incident angles irradiation crystal, and it reproduces maximum S R and minimum data page D2 (as shown in Figure 5) and servo figure 1,3,4,5 of crosstalking.As shown in Figure 9, servo figure 1 and 3 shows same intensity, and servo figure 4 and 5 shows same intensity.
Be familiar with these professional people and understand that other method also goes for regulating the incident angle of reference beam.For example, can hang voice coil motor or stepper motor rotating crystal to regulate incident angle.
According to principle of the present invention, servo block is also applicable to wavelength multiplexing.It is multiplexed that this application class is similar to above-mentioned angle.Specifically, in case the minimum wavelength spacing is decided, each servo block can be by W/2 spacing record, and each data page is pressed W spacing record.Determine that the details of minimum wavelength spacing knows for those skilled in the art.For example, the minimum frequency spacing announced of people's article " body holographic recording system: method and structure " such as Hong is:
〔2πΔν/(c/n)〕(1+cosθr)
ν=light frequency wherein, θ r=reference angle, n=crystal refractive index.In addition, different servo blocks can be by a kind of multichannel multiplexing method record, i.e. angle multichannel multiplexing method or wavelength multiplexing method.Angle is multiplexed can use or mix use respectively with two kinds of methods of wavelength multiplexing.
For being familiar with this professional personnel, under the condition that does not depart from spirit of the present invention, an above-mentioned preferred embodiment is obviously allowed multiple change and remodeling, scope of the present invention is indicated particularly by following claims.The description in addition and the content of announcement only are used to illustrate the present invention, limit the scope of the invention and should not be regarded as, and scope of the present invention is more specifically indicated by following claims.

Claims (29)

1. hologram recording method in photorefractive media, the step that it comprises has:
The a plurality of servo blocks of record in the image space of photorefractive media; With
The a plurality of data pages of record in the image space of photorefractive media.
2. the method for claim 1, wherein each servo block provides position feedback information, utilize servo block reference beam and servo block object beam irradiation photorefractive media, cause the migration of electric charge in this medium and make servo block, each servo block reference beam and servo block object beam incide this dielectric surface with the servo block reference angle, the angle between this servo block reference angle regulation servo block reference beam and the servo block object beam.
3. the method for claim 1, wherein each data page is determined by an interference grating, utilize data page reference beam and data page object beam irradiation photorefractive media, cause the migration of electric charge in this medium and make interference grating, each data page reference beam and data page object beam incide this dielectric surface with the data page reference angle, the angle between this data page reference angle specified data leaf reference light beam and the data page object beam.
4. the method for claim 1 also comprises this step, and a plurality of servo blocks are transformed into a plurality of permanent holograms, and these holograms will can not wiped by this medium of irradiation subsequently.
5. the method for claim 4, wherein this step that a plurality of servo blocks are changed also comprises the step to this medium heating.
6. the process of claim 1 wherein that servo block provides the approach that reproduces one page in a plurality of data pages, do not have crosstalking in this one page basically from other data pages.
7. the process of claim 1 wherein that each servo block is positioned at around the image space of this medium.
8. the method for claim 2, wherein servo block object beam and servo block reference beam are produced by a relevant monochromatic source.
9. the method for claim 3, wherein data page object beam and data page reference beam are produced by that relevant monochromatic source.
10. the method for claim 2, wherein spacing is about 1/2nd of the minimum angular separation of this medium between two servo block reference angles.
11. the method for claim 3, wherein spacing is the minimum angular separation of this medium between two data leaf reference angles.
12. the method for claim 1 also is included in the step of document image space identifier in each image spaces of a plurality of image spaces in this medium, each image space identifier provides the approach of an image space of identification.
13. the method for claim 12 also comprises this step, and the image space identification turn is become permanent holograms, these holograms can not wiped by this medium of irradiation subsequently.
14. the hologram recording method in photorefractive media, the step that it comprises has:
Record first servo block in this medium, first servo block is determined by first interference grating, utilize first reference beam and first object beam to shine this medium, cause the migration of electric charge in this medium and make first interference grating, the first servo block reference beam and the first servo block object beam incide the surface of this medium with the first servo block reference angle, and the first servo block reference angle is stipulated angle between the first servo block reference beam and the first servo block object beam;
Record second servo block in this medium, second servo block is determined by second interference grating, utilize second reference beam and second object beam to shine this medium, cause the migration of electric charge in this medium and make second interference grating, the second servo block reference beam and the second servo block object beam incide the surface of this medium with the second servo block reference angle, and the second servo block reference angle is stipulated angle between the second servo block reference beam and the second servo block object beam;
Record the 3rd servo block in this medium, the 3rd servo block is determined by the 3rd interference grating, utilize the 3rd reference beam and the 3rd object beam to shine this medium, cause the migration of electric charge in this medium and make the 3rd interference grating, the 3rd servo block reference beam and the 3rd servo block object beam incide the surface of this medium with the 3rd servo block reference angle, and the 3rd servo block reference angle is stipulated angle between the 3rd servo block reference beam and the 3rd servo block object beam;
Record the 4th servo block in this medium, the 4th servo block is determined by the 4th interference grating, utilize the 4th reference beam and the 4th object beam to shine this medium, cause the migration of electric charge in this medium and make the 4th interference grating, the 4th servo block reference beam and the 4th servo block object beam incide the surface of this medium with the 4th servo block reference angle, and the 4th servo block reference angle is stipulated angle between the 4th servo block reference beam and the 4th servo block object beam;
Record the 5th servo block in this medium, the 5th servo block is determined by the 5th interference grating, utilize Wucan to examine light beam and the 5th object beam shines this medium, cause the migration of electric charge in this medium and make the 5th interference grating, the 5th servo block reference beam and the 5th servo block object beam incide the surface of this medium with the 5th servo block reference angle, and the 5th servo block reference angle is stipulated angle between the 5th servo block reference beam and the 5th servo block object beam;
Record first data page in this medium, first data page is determined by the first data page interference grating, utilize the first data page reference beam and the first data page object beam to shine this medium, cause the migration of electric charge in this medium and make the first data page grating, the first data page reference beam and the first data page object beam incide the surface of this medium with the first data page reference angle, and the first data page reference angle is stipulated angle between the first data page reference beam and the first data page object beam;
Record second data page in this medium, second data page is determined by the second data page interference grating, utilize the second data page reference beam and the second data page object beam to shine this medium, cause the migration of electric charge in this medium and make the second data page grating, the second data page reference beam and the second data page object beam incide the surface of this medium with the second data page reference angle, and the second data page reference angle is stipulated angle between the second data page reference beam and the second data magnetic object beam; And
Record the 3rd data page in this medium, the 3rd data page is determined by the 3rd data page interference grating, utilize the 3rd data page reference beam and the 3rd data page object beam to shine this medium, cause the migration of electric charge in this medium and make the 3rd data page grating, the 3rd data page reference beam and the 3rd data page object beam incide the surface of this medium with the 3rd data page reference angle, and the 3rd data page reference angle is stipulated angle between the 3rd data page reference beam and the 3rd data page object beam;
15. the method for claim 14 also comprises this step, each servo block is transformed into not the hologram that can be wiped by irradiation subsequently.
16. the method for claim 14, wherein second servo block and the 3rd servo block provide position feedback information at the first data page reproduction period.
17. the method for claim 14, wherein the 4th servo block and the 5th servo block provide position feedback information during second data reproduction.
18. the method for claim 14, wherein each servo block by one in five figures determine.
19. the method for claim 18, wherein each in five figures be recorded in image space around.
20. the method for claim 18, wherein each in five figures is determined by the arrangement of five hot spots.
21. the method for claim 14, wherein in reference beam, object beam, data page reference beam and the data page object beam each light beam with identical wavelengths travel.
22. the method for claim 14, two wherein adjacent data pages are recorded on the angular separation of the minimum angular separation of crystal.
23. the method for claim 14, two wherein adjacent servo blocks are recorded on the angle increment of about 1/2nd minimum angular separation.
24. the reproducting method of the hologram in image space that is recorded in photorefractive media, the step that it comprises has:
The a plurality of servo blocks of record in the image space of this medium, each servo block comprises position feedback information and is determined by an interference grating, utilize servo block reference beam and servo block object beam to shine this medium, cause the migration of electric charge in this medium and make this interference grating, each servo block reference beam and servo block object beam incide the surface of this medium with the servo block reference angle, angle between this servo block reference angle regulation servo block reference beam and the servo block object beam;
In a plurality of servo blocks each is transformed into permanent spatial variations refractive index refraction figure in the medium, and these figures can not wiped by irradiation subsequently;
The a plurality of data pages of record in the image space of this medium, each data page is determined by an interference grating, utilize data page reference beam and data page object beam to shine this medium, cause the migration of electric charge in this medium and make this interference grating, each data page reference beam and data page object beam incide the surface of this medium, angle between this data page reference angle specified data leaf reference light beam and the data page object beam with the data page reference angle;
The data page reference beam is propagated into the surface of this medium with reference angle, list at detector array and reproduce one of them data page and position feedback information; And
Adjust the data page reference angle according to position feedback information.
25. the hologram recording method in photorefractive media, the step that it comprises has:
The a plurality of servo blocks of record in the image space of this medium, each servo block comprises position feedback information and is determined by an interference grating, utilize servo block reference beam and servo block object beam to shine this medium, cause the migration of electric charge in this medium and make this interference grating, each servo block reference beam and servo block object beam incide the surface of this medium with the servo block reference angle, and have the servo block reference wavelength; With
The a plurality of data pages of record in the image space of this medium, each data page is determined by an interference grating, utilize data page reference beam and data page object beam to shine this medium, cause the migration of electric charge in this medium and make this interference grating, each data page reference beam and data page object beam incide the surface of this medium with the data page reference angle, and have the data page reference wavelength.
26. the method for claim 24, wherein the servo block reference angle between each servo block reference beam and each the servo block object beam remains unchanged.
27. the method for claim 24, wherein the data page reference angle between each data page reference beam and each the data page object beam remains unchanged.
28. an equipment that is used for the position feedback information hologram of search records in the image space of photorefractive media, it comprises:
Produce beam device;
The device that light beam is divided into object beam and reference beam;
The spatial light modulator of modulator light beam;
With angle between the two is that the object beam and the reference beam of reference angle incides lip-deep optical devices of this medium;
Detector array, it is transformed into electric signal with light signal; And
The receiving position feedback information is also adjusted the device of reference angle according to position feedback information.
29. a method that is used for the hologram of search records in a plurality of image spaces of photorefractive media, the step that it comprises has:
The a plurality of servo blocks of record in the image space of this medium, each servo block comprises position feedback information and is determined by an interference grating, utilize servo block reference beam and servo block object beam to shine this medium, cause the migration of electric charge in this medium and make this interference grating, each servo block reference beam and servo block object beam incide a surface of this medium with the servo block reference angle, angle between this servo block reference angle regulation servo block reference beam and the servo object beam;
With each is transformed into permanent spatial variations refractive index refraction figure in this medium in a plurality of servo blocks, these figures can not wiped by irradiation subsequently;
Image space identifier of record in each image space, each identifier provides the approach of an image space of identification;
The a plurality of data pages of record in the image space of this medium, each data page is determined by an interference grating, utilize data page reference beam and data page object beam to shine this medium, cause the migration of electric charge in this medium and make this interference grating, each data page reference beam and data page object beam incide the surface of this medium, angle between data page reference beam specified data leaf reference light beam and the data page object beam with the data page reference angle;
The data page reference beam is propagated into the surface of this medium with reference angle, list at detector array and reproduce in the image space data page and position feedback information; And
Adjust the data page reference angle according to position feedback information.
CN97190501A 1996-05-10 1997-05-07 Position feedback system for volume holographic storage media Pending CN1193390A (en)

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US5777760A (en) 1998-07-07
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